3. Field Conditions

  • Select an open area that allows flat horizontal sights up to several hundred feet in opposite directions to minimize pointing errors.
  • A distinct vertical sighting mark at least 30° above the horizon will be needed. A vertical wall works well, although heat waves could be an issue on a sunny day.
  • Make sure support hardware is in good operating condition.
  • Clear parallax in the main telescope and the optical plummet scope.